Gathering Data for Value Stream Mapping
On cycle times, changeover times, uptime, number of operators at each station and other useful details
Say you’re in the process of creating a value stream map. As with any map, you can’t draw it until you’ve gathered all the relevant data.
Identify the baseline
So first, you gather the baseline data you’ll use to plan your process improvements. Data gathering is a three-step process:
- you gather the data,
- draw the shell of the map, and then
- flesh out the information it contains.
Gathering data requires tools, which include a clipboard with each process listed, a stopwatch, a list of questions you can use to obtain relevant data, and — in some situations — a video camera.
Value stream mapping requires specific data — cycle times, changeover times, uptime, number of operators at each station, inventory amounts, batch sizes, working time, and defect rate.
To gather this data, you observe workers doing their jobs. You first watch those completing the last step in the process and work your way back to the start.
While watching workers, ask them questions about the process. They know the process better than anyone. For example, if you want to find out about information flows, ask workers how they’re informed about what to work on next, how often they receive a schedule, how they pass work on once it’s completed, and how they access new components.
Consider a situation where a process improvement team for a large electronics manufacturer targets the cell phone battery manufacturing process and begins gathering data for a current-state value stream map.
The team documents that 2,000 batteries are delivered every week to the manufacturer’s two main customers, the warehouse has three weeks of stored inventory, and delivery details are e-mailed to customers.
The team walks through the process from the end to the beginning — from packaging, to testing, formation, cell assembly, and finally electrode coating. For each step, the team documents the number of operators, cycle times, inventory numbers, changeover times, and uptimes for equipment.
Workers tell the team that the production manager delivers the daily schedule in person to workers in all areas except packaging.
After you’ve gathered the relevant information, like the team in the electronics company, you’re ready to begin mapping the current state.
As a member of a process improvement team you also need to know what information to gather when working with service-based businesses. Unlike in manufacturing, in service delivery, understanding key flows is necessary before attempting any process improvement. These key flows include the time flow, so it’s useful, for example, to ask how long workers need to pack a delivery truck.
Process flows are another key flow, for example, it’s important to find out how many trucks you have to make deliveries. Equally important is information flow — determining how information is delivered. People and communication flows enable you to determine who does what and when.
And now you know, the how, the what, and the why of data gathering for value stream mapping.